Catalysts containing oxides of iron, bismuth and molybdenum, promoted with suitable elements, have long been used for conversion of propylene and/or isobutylene at elevated temperatures in the presence of ammonia and oxygen to manufacture acrylonitrile and/or methacrylonitrile. In particular, Great Britain patent 1436475; U.S. Pat. Nos. 4,766,232; 4,377,534; 4,040,978; 4,168,246; 5,223,469 and 4,863,891 are each directed to bismuth-molybdenum-iron catalysts which may be promoted with Group II elements to product acrylonitrile. In addition, U.S. Pat. Nos. 5,093,299, 5,212,137, 5,658,842 and 5,834,394 are directed to bismuth-molybdenum promoted catalysts exhibiting high yields to acrylonitrile. These catalysts may provide increased acrylonitrile production but with a corresponding decrease in yield of hydrogen cyanide and/or acetonitrile coproducts.